Technical Field
The present invention relates to a narrow-angle directional microphone.
Related Art
The inventor of the present application invented a narrow-angle directional microphone having a primary sound pressure gradient microphone element (hereinafter, the microphone element may be simply referred to as “microphone element”) built in an acoustic tube, and previously filed a patent application (see JP 6-81352 B2).
In the narrow-angle directional microphone described in JP 6-81352 B2, a front acoustic terminal and a rear acoustic terminal of the primary sound pressure gradient element are acoustically connected in a clearance formed between an outer peripheral side of the element and an inner peripheral side of the acoustic tube.
The acoustic terminal is a position of air that effectively provides a sound pressure to a microphone unit, in other words, the acoustic terminal is a central position of air moving at the same time with a diaphragm included in the microphone unit.
If the acoustic connection is made sparse, the directivity gets close to omni-directivity, low-range sensitivity becomes low, low-range directivity becomes broad, and wind noise is more likely to occur. If the acoustic connection is made dense, the directivity gets close to bidirectivity, the low-range sensitivity becomes high, the low-range directivity becomes narrow, and the wind noise is less likely to occur. Therefore, if the degree of the acoustic connection can be changed, sounds can be collected under a setting adapted to an environmental condition.
The present invention includes, as described below, a dual tube structure in which the acoustic tube is held in a microphone case. A narrow-angle directional microphone including the dual tube structure is known in JP 6-48294 U, and the like.